Stored energy combustors have long been utilized for producing hot gases of combustion under pressure to operate turbines. In such stored energy combustors, a carbonaceous fuel is typically combusted with an oxidant to produce hot gases of combustion, and additional fuel may typically be introduced into the hot gases of combustion to be vaporized, or partly decomposed, or both. By so doing, the volume of hot gas can be increased while bringing the temperature of the combustion gas down to a temperature incapable of causing damage to the turbine.
Generally speaking, it has been known that a stored energy combustor may utilize swirling oxidant to generate recirculation zones to provide continuous ignition. Typically, the size of the inner recirculation zone, which is generally known to be critical, is a strong function of swirl blade angle. In this connection, it is known that the size of the generated recirculation zone is increased by an increased swirl blade angle.
In fact, one of the swirler's primary functions is to induce combustion products to flow upstream. There, the combustion products meet and merge with incoming fuel and oxidant. In typical applications, there is little or no recirculation generated where there is weak swirl.
However, when the swirl number is increased to a point where it reaches a critical value, e.g., a swirl number greater than 0.6, the static pressure in the central core just downstream of the swirler becomes low enough to create flow recirculation. Typically, to achieve a strong inner recirculation zone, swirl blade angles are generally in the range of approximately 45.degree. to 60.degree. and, if a significantly smaller angle is utilized, there is weak swirl with little or no inner recirculation.
As is known in accordance with conventional theory, this would ordinarily result in producing unsatisfactory combustion. It is also known that a stored energy combustor should ideally be extremely compact and lightweight, which means that it is essential to generate an expansive inner recirculation zone to provide highly satisfactory continuous ignition and consequent high levels of performance in the combustor. As a result, it would be thought that swirl blade angles on the order of 45.degree. to 60.degree. would be most highly advantageous for this purpose.
However, in actual tests, the inner recirculation zone was found to be too small to avoid significant ignition difficulties. Thus, theory was not borne out in practice when it came to stored energy combustors of compact volume. As a result, it has remained to provide a stored energy combustor having an entirely satisfactory inner recirculation to achieve the objective of continuous ignition.
The present invention is directed to overcoming one or more of the foregoing problems and achieving one or more of the resulting objects.